1. Field of the Invention
The present invention relates to an engaging structure of a fuel cap and a filler neck pipe for a fuel pouring inlet of automobile.
The present application is based on Japanese Patent Application No. Hei. 10-333160, which is incorporated herein by reference.
2. Description of the Related Art
A filler neck pipe extending from a fuel tank has an opening toward the fuel pouring inlet of automobile, and the opening is screwed in engagement with the fuel cap. In short, a first screw threaded in an outer periphery of the fuel cap and a second screw threaded in an inner periphery of the filler neck pipe are engaged, so that a sealing part of a fuel cap is fast to the opening of the filler neck-pipe so as to close the opening of the filler neck pipe and prevent a fuel steam from volatilization. The filler cap is,when pouring the fuel, taken off from the filler neck pipe by rotating the fuel cap, e.g., in a counterclockwise direction, and if, after pouring the fuel, the fuel cap is put on the opening of the filler neck pipe and is rotated, e.g., in a clockwise direction, the opening of the filler neck pipe is closed.
When fastening the fuel cap onto the opening of the filler neck pipe, the fastening should go on until the sealing portion of the fuel cap is fast to the opening of the filler neck pipe and is exactly sealed.
Fuel caps housing therein torque detecting mechanism and sound mechanism have recently been known. In the fuel cap having the torque detecting mechanism, when rotating the fuel cap until a necessary tightening amount that the sealing part of the fuel cap is closely attached to the opening of the filler neck pipe, the torque detecting mechanism works to cause the fuel cap to run idle and cause the sound mechanism to issue a sound to notify with a sound that the fuel cap is tightened up to the necessary tightening amount. An operator can recognize thereby that the fuel cap is exactly tightened, and a dullness or loosening of the sealing portion by over-tightening can be prevented.
Since pressure of the fuel steam in a fuel tank is increased at high temperature time in midsummer, the fuel steam or the fuel may be spouted at once from the opening of the filler neck pipe at the same time when the fuel cap is removed. So, in conventional structures of the fuel pouring inlet, an engaging distance between the first screw part in the fuel cap and the second screw part in the opening of the filler neck pipe is lengthened to make difficult rapid opening of the cap so that the fuel steam slowly discharged from a space between both until taking off the fuel cap so as to prevent abrupt spouting of the fuel steam.
Incidentally, if the engaging distance between the first screw part of the fuel cap and a second screw part in the opening of the filler neck pipe is lengthened, such a problem will arise that a person easily misunderstands that the screwing is finished before the torque detecting mechanism works. In this case, the sealing property of the cap is insufficient to allow the fuel steam to run away in an atmospheric air.
On the other hand, if the engaging distance between the first screw part and the second screw part is shortened, it is easy to open and close the cap, but the inconveniences as mentioned above are easy to occur.